Summary A Beech 95 Travel Air, C-FCNU, serial number TD668, was on a local training flight practising simulated single-engine procedures in the circuit for Runway18 at Winnipeg International Airport. Shortly after the aircraft was turned onto the final approach to Runway18, near the end of a scheduled one-hour training session, the aircraft made a rapid uncontrolled descent and struck the embankment of a ditch on the north side of Jefferson Avenue in Winnipeg, Manitoba. The aircraft bounced and came to rest approximately 70feet northwest of the initial point of impact, 2.4nautical miles short of the runway. A post-crash fire broke out that consumed most of the centre wing and cabin sections of the aircraft. The aircraft was destroyed. The two pilots, the only occupants of the aircraft, sustained fatal injuries. The crash occurred during daylight hours at 0954 central daylight time. Ce rapport est galement disponible en franais. Other Factual Information The aircraft, C-FCNU, was being used for multi-engine, flight-training exercises. It had accumulated approximately 13784hours total airframe time and, according to a review of available documentation, was certificated, equipped and maintained as required by existing regulations and approved procedures. The aircraft's weight and centre of gravity for take-off were calculated to have been within the certified limits. C-FCNU was not equipped with a flight data recorder or cockpit voice recorder; they were not required by regulations. The instructor pilot and student pilot were both properly qualified for the training flight. The instructor held a valid Canadian airline transport pilot license, with a GroupI instrument rating and ClassII Instructor rating. The student pilot held a valid Canadian commercial pilot license. The occurrence flight was the first flight of the day for both pilots, and a review of the company's dispatch logs revealed that both pilots were adequately rested. The flight was scheduled to include engine-failure recovery and single-engine approach-to-landing exercises. These exercises are included in the Transport Canada-approved company training curriculum. On this particular flight, the training was to be accomplished under visual flight rules, whereby the pilot has visual reference to the ground and other air traffic in the area. The weather report for Winnipeg for 10001, six minutes after the accident, states the following: winds 120degrees at 5knots; visibility 15statute miles; a few clouds at 25000feet; temperature 13degrees Celsius; and dew point 6degrees Celsius. At 0851, C-FCNU was cleared for take-off and the crew proceeded with the training session as planned. They flew a series of touch-and-go landings for approximately one hour. At approximately 0952, the Winnipeg tower controller advised the crew of C-FCNU that their traffic position was number2 to land followed by the words waketurbulence. An AirbusA320 was in front of them, cleared to land. The instructor acknowledged that he had received and understood the tower controller's instruction. This was the last communication received from C-FCNU. At 0952, the occurrence aircraft was on final approach to Runway18 at approximately 500feet above ground level (agl) in a normal approach attitude. Suddenly the aircraft pitched up, rolled rapidly, and entered a very steep dive in the opposite direction, a manoeuvre similar to a spin or stall. Radar data for this time show the aircraft decelerated from 130to 100mph at an altitude of 1300feet above sea level (asl), approximately 500agl. At 0953:18, radar contact was lost at a position coincident with the occurrence site. The wreckage trail and associated ground scarring indicated that the aircraft struck the north side of Jefferson Avenue on a heading of approximately 310degrees in a wings-level, approximately 5degree nose-down attitude. It then struck the far side of the adjacent ditch, bounced into the air, travelled about 70feet on a track of 310degrees and came to rest facing 030degrees. The aircraft burst into flames on impact. The landing gear and both propellers were torn off at impact with the ditch and remained within 30feet of each other. The right propeller was almost completely imbedded in the soil of the ditch embankment. The landing gear would have had to be in the extended position for it to tear off. All of the cockpit engine power controls were destroyed. On-site inspection of the remaining aircraft components revealed three anomalous factors: the rudder trim had 15units of right trim input selected; the left mixture cable was in the idle cut-off position; and, the left magneto switch was in the Off position. The positions of the remaining engine and propeller control cables were consistent with the settings for maximum power. Most of the aircraft, including the aircraft's cockpit and a large portion of the centre fuselage section, was destroyed by a post-crash fire. There were no avionics or instruments intact that could provide any useful information. Most of the aircraft's mechanical, hydraulic and electrical systems were destroyed. The propeller blades were damaged and scored and had separated from the engine at the crankshaft flanges due to a combination of shear and tensile overload forces. Wreckage information, primarily the ground scarring, indicates that the aircraft was in the process of recovering from a very steep dive when the impact with the ditch occurred. Autopsy results indicated that both pilots perished from deceleration injuries before the aircraft was consumed by fire. The nature of the instructors' injuries suggested that he was at the controls at the time of impact. There was no evidence of smoke inhalation or any medical condition which might have caused pilot incapacitation. Toxicology reports revealed no substance that could have caused impairment of either pilot. The minimum airborne control speed (Vmca) listed in the Beech95 operators manual is 80mph. However, Beechcraft has published an additional speed limitation associated with single-engine operations specific to simulated engine failure training. This limitation is referred to as velocity safe single engine (Vsse) and is listed in Perimeter Aviation's procedures as 100mph minimum. Perimeter Aviation directs their instructors to use this, or an even higher minimum speed of 108mph, when practising single-engine drills. Transport Canada Air Carrier Advisory Circular, 0051 93-06-22, and TSB Recommendation 92-03 refer to this aircraft type's tendency to enter into spins at low airspeeds. These reports identify this tendency as a potential safety issue and emphasize the need for heightened awareness of it. Following this accident, flight tests were carried out using an identically equipped and configured Beech95 aircraft in similar atmospheric conditions. When the landing gear was selected down, with a simulated power loss of the left engine, there was an airspeed loss of approximately 30mph. Perimeter Aviation's training program requires that one actual in-flight shutdown be accomplished during the course of a student's multi-engine training. Company records indicate that this had been done with the occurrence student on September26. There was also a company procedure that precluded an intentional in-flight engine shutdown, for training purposes, near an airport. Another procedure required that company maintenance be advised if such an engine shutdown was scheduled. In this occurrence, maintenance personnel had not been so advised. Although C-FCNU was not under radar control, it did have an operational transponder which allowed its movements to be recorded by radar. Radar data analysis showed the following. C-FCNU was following approximately two miles behind an Airbus320 aircraft. C-FCNU's airspeed decreased from 130to 100mph in approximately 15seconds immediately before the radar image disappeared from the radar screen. An airspeed reduction of this magnitude at this point in the circuit is similar to the airspeed decrease exhibited when the landing gear is selected down with a simulated power loss of one engine. The last positive radar contact with C-FCNU coincides closely with the location of the wreckage site. The last observed radar position of C-FCNU was approximately 200feet lower than the preceding Airbus320 at the same point on the approach. The radar data do not show an end to the aircraft's deceleration or the aircraft stabilizing at an airspeed above 100mph. Such an airspeed stabilization would indicate that this rapid deceleration was a scheduled segment of the approach and that it would have eliminated control loss due to airspeed decay as a factor in this accident. Transport Canada's Aeronautical Information Publication (AIP) Canada states: Wake turbulence is caused by wing tip vortices and is a by-product of lift. The greatest vortex strength occurs under conditions of heavy weight, clean configuration, and slow speed. One should avoid the area below and behind other aircraft, especially at low altitude where even a momentary wake turbulence encounter could be disastrous. ...wake turbulence can persist for periods in excess of two minutes, it normally descends after it is produced, and it will last longer in calm wind conditions; aircraft flying into the core of a wingtip vortex can experience a rapid vortex-induced roll in the direction of the vortex air flow; and, small aircraft encountering large vortices may not be able to recover. There are no mandatory wake turbulence separation criteria for arriving aircraft operating under visual flight rules. Wake turbulence avoidance is the pilot's responsibility when operating under these circumstances. The only air traffic control (ATC)procedure for arriving VFR aircraft is that a light aircraft landing behind a medium weight category aircraft be cautioned as to the possibility of encountering wake turbulence on approach to the runway. Such a caution was the last communication that ATC issued to the pilots of C-FCNU. The recommended pilot technique for avoiding wake turbulence is to fly the approach higher than the preceding aircraft's approach, and plan to land past the point where the preceding aircraft touched down.2 The crew of C-FCNU did not follow this technique; they flew a lower approach profile, which put them below the preceding aircraft's approach path. Pilot task and thought process workload increases considerably during intensive training compared to routine non-training flights. Aviation psychology research has shown that when cockpit workload is increased, pilots make more attention-based errors - forgetting to carry out intended actions or not noticing abnormalities. The combined effect of these errors is often referred to by human factors experts as a decreased level of situational awareness.3